Shadow-mask cathode-ray tube including a masking member comprising a skirt having indentations and projections overlapping and attached to a frame

ABSTRACT

A cathode-ray tube including an envelope comprising an outwardly domed generally rectangularly shaped faceplate, a phosphor screen disposed on the internal surface of said faceplate, means for projecting electrons towards the screen, and a generally rectangularly shaped shadow-mask assembly mounted adjacent to the screen in the path of the electrons. The mask assembly comprises a rigid metal frame and a metal masking member welded to the frame. The masking member includes a domed shadow mask integral with a peripheral skirt having a plurality of alternate projections and indentations, which may extend the length of the skirt substantially parallel to the longitudinal axis of the tube.

United States Patent [72] Inventor Kenneth AdelpeI-t Long Lancaster, Pa.

[21] App1.No. 46,246

[22] Filed June 15, 1970 [45] Patented June 15, 1971 [7 3] Assignee RCA Corporation 54] QHRQW-MASKEAIHQPEBAYT B INCLUDING A MASKING MEMBER COMPRISING A SKIRT HAVING INDENTATIoNs AND PROJECTIONS OVERLAPPING AND ATTACHED TO A FRAME 6 Claims, 8 Drawing Figs.

[52] US. Cl 313/85, 29/2517, 313/286, 313/292: [51] Int. Cl H01j l/96, H0lj9/l8,l-l0lj29/46 [50] Field of Search 313/64, 85, 92 B Primary ExaminerRoy Lake Assistant Examiner-V. Lafranchi Attorney-Glenn H. Bruestle [5 6] References Cited UNITED STATES PATENTS 2,795,718 6/1957 Van Hekken et a1 313/85 2,897,392 7/ 1959 Fiore. 313/92 3,296,850 l/1 967 Fiore 72/351 3,351,996 11/1967 Fiore 29/2513 3,404,302 10/1968 Nicklas...; 313/85 l1/1969 Mears ABSTRACT: A cathode-ray tube including an envelope comprising an outwardly domed generally rectangularly shaped faceplate, a phosphor screen disposed on the internal surface of said faceplate, means for projecting electrons towards the screen, and a generally rectangularly shaped shadow-mask assembly mounted adjacent to the screen in the path of the electrons. The mask assembly comprises a rigid metal frame and a metal masking member welded to the frame. The masking member includes a domed shadow mask integral with a peripheral skirt having a plurality of alternate projections and indentations, which may extend the length of the skirt substantially parallel to the longitudinal axis of the tube.

PATENTEU JUHI 51971 3; 585.431

.SHEU a or 4 PATENTEU JUN] 519m SHEET 0F 4 AND ATTACHED TO A FRAME BACKGROUND OF THE INVENTION This invention relates to a novel cathode-ray tube and particularly, but not exclusively, to a shadow-mask color-television-picture tube.

Color-television-picture tubes of the shadow-mask type (also called aperture-mask type) usually comprise a mosaic screen of phosphor elements, means including an electron gun for exciting the screen, and a shadow-mask assembly positioned between the electron gun and the screen. The shadowmask assembly includes a thin-apertured metal masking member, a frame for supporting the masking member, and frame mounting means for supporting the masking member adjacent to and in a predetennined spaced relationship with the elements of the mosaic screen.

In some prior shadow-mask color-televisiOn-picture tubes, the mosaic screen and the masking member are generally rectangular, with rounded corners, and have outwardly bowed sides. In one form, the masking member comprises a domed, apertured mask. and a substantially imperforate peripheral skirt integral with the mask. The skirt is substantially normal to the plane of the mask and is attached, as by welding, at a limited number of points to a rectangular support frame. The frame has a substantially L-shaped cross section, and the four sides of the frame may be curved so that they are substantially parallel to the curvature of the domed maski Although the prior-art mask skirt is ideally formed straight and normal to the plane of the mask, in practice it curls or angles from the desired position. When welding the skirt to the frame, the curled or angled skirt does not lie flat on the sur face of the frame and must be pressed against the frame. Pressing the curled or angled skirt distorts the contour of the mask and leaves a residual stress. This distortion and the residual stress remain in the mask and may adversely affect the color purity of the image displayed on the screen when the tube is operated.

SUMMARY OF THE INVENTION The novel cathode-ray tube includes an envelope, a mosaic phosphor screen, an electron-gun means, and a shadow-mask assembly comprising an apertured, domed masking member and an integral peripheral skirt welded to a metal frame at a limited number of points as in the prior art. Unlike the prior art, the skirt has a plurality of alternate projections and indentations or flutes therein. The projections and indentations may extend the length of the skirt and substantially parallel to the longitudinal axis of the tube.

Making the skirt with projections and indentations in the skirt forms and draws the metal in a manner which reduces or eliminates curling and angling of the skirt. As a result, the skirt lays substantially flat against the frame during the welding of the mask to the frame, thereby eliminating the need for counteracting any curl or angling of the skirt, reducing or eliminating distortion of the mask contour, and reducing residual stress in the mask.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal view partly in section of a novel cathode-ray tube embodying the invention.

FIG. 2 is a plan view partially in cross section of the shadowmask assembly ofthe novel tube of FIG. 1.

FIG. 3 is an enlarged detail view ofa portion of the mask assembly of FIG. 2 for a l9 inch color-television-picture tube.

FIG. 4 is a broken-away perspective view of a portion of the novel tube of FIG. 1 illustrating the aperture-mask assembly.

FIG. 5 is an enlarged detail view of a portion of the shadowmask of FIG. 2 for a 25-inch colOr-teIevision-picture tube.

FIGS. 6A and 6B are an enlarged broken-away sectional detail view of a portion of the novel tube of FIG. 1 and of a prior-art tube.

FIG. 7 is an enlarged broken-away perspective view illustrating an alternative construction for the novel tube of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a shadow-mask-type color-picture tube 10 comprised of an envelope ll including a neck 12, a panel 13, and an interconnecting funnel 14 along a longitudinal axis C-C. The panel 13 includes an outwardly domed generally rectangularly shaped faceplate l5 and panel sidewall 16. A screen 17 comprised of a multiplicity of phosphor clots, formed in a manner well known in the art, is supported on the internal surface of the faceplate 15. An electron-gun means 18 for projecting electrons towards the screen 17, which may be a conventional tricolor electron gun 18, is positioned in the neck 12. The electron gun 18 is adapted to project three electron beams 19a, 19b, and 19c towards the screen 17.

A generally rectangular shadow-mask assembly 20 is positioned in the envelope 11 between the electron-gun means 18 and the screen 17 adjacent to, and substantially parallel to, the screen 17. The assembly 20, which is shown in FIGS. 1, 2 and 3, comprises a rigid metal support frame 21, four clip plates 22 (22a through 22d in FIG. 2), four support straps and a metal asking member 24. The clip plates 22 are attached to the frame 21, and the support straps 23 are attached at one end to the clip plate 22. The other end of the support straps 23 is provided with suitable apertures into which support studs 25 are received. Four electrode support studs 25 extend from the internal surface of the panel sidewall 16 at locations about midway between the corners thereof.

Referring to FIGS. 1 and 2, the frame 21 preferably comprises an endless strip of metal formed in a generally rectangular shape having short sides 26a and 27b, and corners 28a through 28d. The strip has a generally L-shaped cross section which is of substantially uniform size along the strip. The L is oriented with a traverse flange 29 extending inwardly from the rear edge of an axial flange30. In the preferred embodiment, each of the sides 26a and 26b and 27a and 27b is bowed outwardly away from the central longitudinal axis CC of the tube and, also, is bowed parallel to the longitudinal axis of the tube towards the screen 17. A preferred frame is known in the art as a barrel-type frame. In a barrel-type frame, the midpoints of the long sides 26a and 26b and the midpoints of the short sides 27a and 27b are substantially planar.

The masking member 24 includes a mask 32 which is generally perpendicular to the axis C-C of the tube integral with a peripheral skirt 3! that is substantially parallel to the axis C-C of the tube and substantially normal to the plane of the assembly 20. The masking member 24 is attached to the axial flanges 30 of the frame 21 and includes a domed mask 32 having a multiplicity of apertures 33 within a field of approximately rectangular configuration surrounded by substantially imperforate border 34. A border fillet 35 is provided at the periphery of the imperforate border 34 between the border portion 34 and the skirt 31.

The skirt 31 is comprised of a plurality of alternate projections 36 and indentations 37, or flutes, which may be formed and drawn using a punch and die in a manner well known in the art. The projections 36 and indentations 37 extend substantially parallel to the longitudinal axis C-C of the tube. This may be accomplished in the same single punch-and-die operation used for forming the domed rectangular shape of the masking member 24.

The dimensions between inside surfaces of the indentations 37 permit the masking member to telescope over the axial flange 30 of the frame 21. The surface of each of the projections 36 and indentations 37 is approximately parallel to the corresponding matching outside surface of the axial flange 30 of the frame 21. The dimensions of the masking member 24 and the frame 21 are preferably such that when the masking member 24 is on the frame 21 there is no more than 0.030 inch of play between the skirt 31 and the frame 21.

EXAMPLE 1 For a 19 inch ultrarectangular color-television-picture tube, the projections 36 and indentations 37 are spaced around the skirt 31 as partially shown in FlG. 3. The skirt 31 is enlarged at four places, hereinafter called the pocket areas 38, to provide clearance where the skirt 31 overlaps the clip plates 22, A pocket area 38 is also formed with projections 36 and indentations 37. The pocket area 38, projections 36 and indentations 37 are better illustrated in FIG. 4.

The projections 36 and indentations 37 or flutes, shown in FIG. 3, are substantially the same width along the outside peripheral surface of the skirt 31. Wide indentations 370 (FIG. 4) are provided in a predetermined pattern on the rectangular short sides 26a and 26b and long sides 27a and 27b, and wide indentations 37b (FIG. 4) are provided on the corners 28a through 28d of the peripheral surface of the skirt 31. The wide indentations 37a and the corner indentations 37b are provided at the attachment points of the skirt 31 and the axial flange 30.

The wide indentations 37a and corner indentations 37b each provide two attachment points. One attachment point is used for initial manufacture, and the other is used for salvage manufacture. The attachment points are asymmetrical preferably for each 180 position of the masking member, thereby providing for reuse ofa salvaged masking member by rotating the masking member I80. The preferred width 41 of the wide indentations 37a of the four sides 26a, 26b, 27a and 27b is 0.750 inch. The indentations 37b on the corners 28 are at least as long as the 90 segment of the corner radius. The corner indentations 37b vary in length somewhat since uniform projections 36 and indentations 37 are spaced between the nearest wide indentations 37a and the corners 28 starting from the nearest wide indentations 37a and spacing projections 36 and indentations 37 until the available space remaining is less than the width of the projections 36 and indentations 37.

The depth 42 between the inside peripheral surface of the projections 36 and the inside peripheral surface of the indentations 37, or the wide indentations 370, or the corner indentations 37b is approximately 0.045 inch. The skirt portion 39 connecting between the projection 36 and the indentations 37 is at an approximate 45 angle to the peripheral sidewall of the indentations 37.

The projections 36 and indentations 37 blend into the border fillet 35 at the periphery of the border portion 34 and the skirt 31. The width 43 of the projections 35 is approximately 0.375 inch, and the width 44 of the indentations 36 is approximately 0.375 inch.

The length of the skirt 31 varies between the short sides 26a and 26b, long sides 27a and 27b, the corners 28. The approximate preferred skirt length on the midpoint of the short sides 26a and 26b (major axis) is 0.417 inch, on the midpoint ofthe long sides 27a or 27b (minor axis) is 0.835 inch, and on the midpoint of the corners 28a through 28d (diagonal axis) is 0.429 inch.

In attaching the skirt 31 to the axial flange 30, it is preferred that 16 attachment points, shown by the arrows in FIG. 3, are used. The skirt 3] is attached to the axial flange 30 by spot welding as is well known in the prior art.

EXAMPLE 2 For a 25 inch ultrarectangular color-picture-tube, the projections 36 and indentations 37 are spaced around the skirt 31 as shown in FIG. 5. The skirt 31 includes pocket areas 38, wide indentations 37a, corner indentations 37b skirt portion 39, and fillets 40 as described in example 1. The skirt 31 ofexample 2 differs from the skirt 31 of example 1 by the size and number of projections 36, indentations 37 and wide indentations 37a.

The depth 42 between the inside surface of the projections 36 and the inside surface of the indentations 37 or the wide indentations 37a or the corner indentations 37b is approximately 0.045 inch. The width 43 of the projections 36 is approximately 0.400 inch, the width 44 of the indentations 37 is approximately O.400 inch, and the width 41 of the wide indentations 36a is approximately 0.875 inch. The skirt 3] of example 2 is spot welded to the frame at 20 attachment points.

In making the novel cathode-ray tube, as previously described, clip plates 22 are first welded to the frame 21. The masking member 24 is then positioned in a telescopic manner over the frame 21 with the skirt 31 overlapping the axial flange 30 in a certain fixed relationship with respect to the clip plates.

In this position, the wide indentations 37a and 37b of the skirt 31 overlap the axial flange 30 by approximately threeeighths inch. The inside surface of the wide indentations 37a and 37b may not be in contact with the frame since the masking member 24 and the frame 21 are manufactured with tolerances as previously described. Therefore, the outer edge of the axial flange 30 may be initially spaced from the adjacent surface of the wide indentations 37a of the skirt 31 at the attachment points.

The skirt 31 is then pressed against the flange 30 so that the wide indentations 37a and corner indentations 37b are substantially in intimate contact with the axial flange 30 at the attachment points.

After the indentations 37a and 37b are in intimate contact with the axial flange 30 of the frame 21, the skirt 31 is attached, such as by spot welding, at the attachment point in a manner which is well known in the art. Preferably each weld 45 is at or below the midpoint of the overlap of the skirt 31 and the axial flange 30 to permit slight radial movement of the masking member 24 away from the outer peripheral surface of the axial flange 30 on thermal expansion and contraction of the parts during warm up.

FIGS. 6A and 6B illustrate the relationship of the masking member 24 and the frame 21 for the tube 10 of theinvention and for a prior-art tube prior to welding the skirt 31 to the frame 30. As shown in FIG. 6A, the skirt 31 of the novel masking member includes projections 36 and indentations 37 is straight and is approximately normal to the plane of the masking member 24, with side indentations 37a and corner indentations 37b substantially parallel to and near or against the matching surface of the axial flange 30 within the tolerances previously described. Thereby, at most, only a minor movement of the skirt 31 occurs in pressing the wide indentations 37a and 37b into intimate contact for subsequent attachment.

As shown in FlG. 6B, the prior-art skirt 31a of the prior-art masking member 24b does not include projections and indentations, and, similarly positioned over the axial flange 30, is not parallel to or near to the matching surface of the axial flange 30. This occurs since the prior-art skirt 31a is not normal to the plane of the prior-art masking member 24b but angles out from the mask. in addition, the prior-art skirt 31a curls outwardly from a straight position as shown in FIG. 6B. In some prior-art tubes, the skirt 31a must be moved as much as approximately three-sixteenths inch at the lower edge to provide intimate contact for subsequent attachment. The actual amount of the lower edge of the skirt 310 must be moved to make intimate contact with the frame 21 is not the same for different skirt lengths but increases with skirt length. When the prior-art skirt 31a is straightened and pressed against the frame 21 in this manner, the domed contour of the masking member 24 is distorted from the desired position by the spring of the metal.

After the masking member 24 is attached to the frame 21, the masking member --frame assembly is positioned in a fixed relationship spaced from the screen 17, and the support straps 23 are attached to the clip plates 22 in a manner well known in the art.

GENERAL CONSIDERATIONS The novel tube may be a color-television-picture tube or may be any other cathode-ray tube which includes a mask assembly having an integrally formed mask and skirt attached to a frame. The electron-gun means, although described as a tricolor three-electron-gun unit, may also be a single-gun unit. Any suitable electron gun which emits an electron beam may be used.

Although a barrel-shaped frame is illustrated for support of the masking member, any suitable support means may be used that can be suitably attached in a manner, as by welding, to the skirt indentations. For example, a spherically shaped frame such as described in U.S. Pat. No. 3,333,134 to RC. Demmy may be used. I

The frame 21 and masking member 24 are preferably both made of cold-rolled steel. It is preferred that the frame be of considerably thicker material than the masking member. For example, in one embodiment of the shadow-mask assembly 20, the frame 21 is made of 0.093 inch, thick material, whereas the masking member is made of 0.006 inch thick material. A relatively thin masking member 24 is very desirable from a practical standpoint because it minimizes electron interception by the sidewalls of the apertures therein. However, the thin masking member is sufficiently rigid to maintain its domed shaped without external support. The provision of a relatively thick, massive frame is highly desirable so as to pro vide a good heat sink to stabilize the operational temperature of the shadow-mask electrode 20 and prevent temperature fluxations of the thin masking member 24.

- The preferred skirt 3] of the masking member 24 in the preferred embodiment is of nonuniform length. Other masking members having skirts of uniform length that include indentations and projections may also be used.

The size, quantity, and location of the projections and indentations in the skirt can vary, especially within different tube sizes, and for different length skirts. Since the masking member, including the skirt, is formed from a flat sheet of metal, the size, quantity, and location of the projections and indentations must be sufficient to result in a straight skirt parallel to the longitudinal axis C-C of the table. Although projections are not shown on the corners of the rectangular shape of the skirt, projections may be used when necessary to form a straight skirt.

Although the depth 42 is preferred to be approximately 0.045 inch, it can be within the range of 0.030 to 0.050 inch. If the depth 42 is larger than 0.050 inch, the material of the skirt may tear during forming, and if the depth is less than 0.030 inch, the skirt is not formed sufficiently to be straight and normal to the plane ofthe assembly.

Although the projections and indentations are preferred substantially parallel to the longitudinal axis of the tube and the full length of the skirt, this is only necessary to economically form the masking member in one operation. Other forms of projections and indentations such as triangular or oval may be used some of which may necessitate multiple forming operations. In addition the projections or indentations need not be'formed the full length of the skirt. HO. 7 illustrates a portion of a skirt where the indentations 37 are formed less than the full length of the skirt. A reversal of the projections 36 and indentations 37 of PK]. 7 would be an example where the projections 36 are formed less than the full length of the skirt. By not extending the indentations 36 the length of the frame, the free edge of the skirt is larger than the periphery of the frame 21 by the depth 42, thereby providing ease of assembly of the skirt 31 over the frame 21.

lclaim:

l. A shadow-mask cathode-ray tube including:

a. an envelope comprising an outwardly domed generally rectangular faceplate,

b. a mosaic phosphor screen disposed on the internal surface of said faceplate c. electron-gun means for pro ecting electrons towards said screen, and

d. a generally rectangular shadow-mask assembly mounted adjacent to said screen in the paths of said electrons, said assembly comprising a rigid metal frame and a thin sheet metal masking member welded at a limited number of points to said frame, said masking member including i. a multiapertured, domed mask integral with ii. a peripheral skirt substantially normal to the plane of said mask, the improvement comprising: said peripheral skirt having a plurality of alternate projections and indentations therein forming means for attaching said skirt to said frame.

2. The tube of claim 1 wherein the faces of said indentations are substantially parallel to said frame, said indentations forming a surface for overlapping attachment to a surface of said frame.

3. The tube of claim 2 wherein said indentations are substantially parallel to the longitudinal axis of said tube and extend the length of said skirt.

4. The tube of claim 2 wherein said projections are substantially parallel to the longitudinal axis of said tube.

5. The tube of claim 4 wherein said projections and indentations are in the range of 0.250 to 0.625 inch wide and in the range of0.030 to 0.050 inch in depth.

6. The tube of claim 1 wherein said projections extend less than the length of said skirt. 

1. A shadow-mask cathode-ray tube including: a. an envelope comprising an outwardly domed generally rectangular faceplate, b. a mosaic phosphor screen disposed on the internal surface of said faceplate, c. electron-gun means for projecting electrons towards said screen, and d. a generally rectangular shadow-mask assembly mounted adjacent to said screen in the paths of said electrons, said assembly comprising a rigid metal frame and a thin sheet metal masking member welded at a limited number of points to said frame, said masking member including i. a multiapertured, domed mask integral with ii. a peripheral skirt substantially normal to the plane of said mask, the improvement comprising: said peripheral skirt having a plurality of alternate projections and indentations therein forming means for attaching said skirt to said frame.
 2. The tube of claim 1 wherein the faces of said indentations are substantially parallel to said frame, said indentations forming a surface for overlapping attachment to a surface of said frame.
 3. The tube of claim 2 wherein said indentations are substantially parallel to the longitudinal axis of said tube and extend the length of said skirt.
 4. The tube of claim 2 wherein said projections are substantially parallel to the longitudinal axis of said tube.
 5. The tube of claim 4 wherein said projections and indentations are in the range of 0.250 to 0.625 inch wide and in the range of 0.030 to 0.050 inch in depth.
 6. The tube of claim 1 wherein said projections extend less than the length of said skirt. 